Abstract : Rocket engines fueled by a dense propellant such as kerosene provide a number of advantages over hydrogen-fueled engines for primary stages. A major problem in the development of liquid fueled rocket engines has been the occurrence of combustion instability. The lack of a detailed understanding of how combustion instability occurs in liquid-fueled rocket engines has resulted in costly engine development programs that must be avoided in the future. The present research program examined the specific effects of atomization in combustion instability. The effects of mean drop size, drop size distribution, and atomization periodicity were examined explicitly with a combustion response model, the results from which indicated that all of these effects were important. It was shown that periodic atomization, in particular, results in large variations in the magnitude of the response when the atomization frequency is on the same order as the acoustic oscillation frequency. Experimental results from a sub-scale rocket combustor that used electro-mechanically forced atomization to accentuate the natural frequency of periodic atomization associated with impinging jet injectors were also undertaken. The presence of forced longitudinal modes, corresponding to the forced atomization frequencies, substantiate the importance of periodic atomization. A conceptual model of this potentially dominant mechanism of combustion instability was also developed as part of the study.